IBM AT 5170 Technical Reference page 146

The dc output-voltage sense signal holds the
I
power-good
I
signal
at a low level when power is switched on until all output voltages
have reached their minimum sense levels. The
I
power-good
I
signal has a turn-on delay of at least 100 milliseconds but not
longer than 500 milliseconds and can drive six standard TTL
loads.
The following figure shows the minimum sense levels for the
output voltages.
Level
(Vdc)
Minimum (Vdc)
+5 +4.5
-5 -3.75
+12 +10.8
-12 -10.4
Sense Level
3-6 Power Supply